1. Field of the Invention
This invention relates to a radiation imaging system for obtaining images two-dimensionally.
2. Related Background Art
In conventional radiation photography, a film screen system made up of sensitized paper and radiation-photographic film in combination is in wide use. According to this method, radiation that has passed through a subject such as a patient contain information about the interior of the subject (xe2x80x9cinterior informationxe2x80x9d), the information is converted into visible light proportional to the intensity of the radiation by means of the sensitized paper, and the radiation-photographic film is exposed to the light to form a radiation image on the film.
Such a film exposure method, however, requires the step of developing the film before a doctor obtains the radiation image of the patient, and has suffered from the problem that the developing step takes much labor and time. In addition, radiation-photographic films obtained by photography must be stored for a certain period in hospitals or doctor""s offices, and the films stored may be enormous in number, causing a great problem for management.
To cope with such problems, recent progress in technology has brought about an increasing demand for the materialization of recording-and-reproduction of radiation image information by means of electric signals, and has already brought forward a proposal for a radiation imaging system in which radiation is converted into visible light proportional to the intensity of the radiation by means of a phosphor, and the light is converted into electric signals by the use of a photoelectric conversion element. This system has begun to be put into practical use.
Such an imaging system used in radiation photography or the like is constituted basically of a fluorescent plate which converts radiation into visible light, a photoelectric conversion element which converts the visible light into electric signals, a substrate on which the photoelectric conversion element is mounted, a base rest which supports the substrate, a circuit board with wiring on which electronic parts for processing the photoelectrically converted electric signals are mounted, and an outer enclosure which holds these constituents.
This is described below with reference to FIG. 15. In FIG. 15, reference numeral 1 denotes a radiation image detection panel which detects radiation and convert it into electric signals. It is constituted basically of a fluorescent plate 1a, a photoelectric conversion element 1b and a substrate 1c. For the substrate 1c of the photoelectric conversion element 1b, glass sheets are widely used because it is required to undergo no chemical action with semiconductor devices, to be durable at the temperatures used in semiconductor processing, and to have dimensional stability.
For the fluorescent plate 1a, a resin sheet coated with a phosphor comprised of a metal compound is used, and the fluorescent plate is unified with the substrate 1c through an adhesive. Where the photoelectric conversion element 1b is required to have moisture resistance, the fluorescent plate 1a and the photoelectric conversion element 1b are sealed with a moisture-impermeable and radiation-transmissive film (not shown) in some cases.
These are fastened to the base rest 4 via a spacer 4a by bonding, thus forming the radiation image detection panel 1. Reference numeral 5 denotes a circuit board on which electronic parts 5a for processing the photoelectrically converted electric signals are mounted, and which is connected with the photoelectric conversion element 1b through a flexible circuit board 6. These are fastened inside a casing 2 and are further closed with a radiation-transmissive casing cover 3. In this way, the radiation imaging system is set up hermetically sealed in an outer enclosure consisting of the casing 2 and the casing cover 3.
Imaging systems of this kind have hitherto been used in radiation imaging systems of a stationary type. In recent years, however, there has also come to be a demand for imaging systems of a portable type which are light-weight and compact so that the photography can be performed rapidly, with high precision and also on various portions of the human body.
Accordingly, in the designing of systems it has come to be taken into consideration that a load is partly applied by a subject (patient) to the casing cover 3, causing the outer enclosure to deform and so to come into contact with the radiation image detection panel 1, breaking the latter, and thus it has come to be required to pay attention also to resistance to deformation under load. Especially for the purposes of protecting the substrate 1c from any impact and vibration applied when thee apparatus is carried and from any possible breakage when dropped, and of preventing the outer enclosure from undergoing deformation due to any load applied at the time of radiation photography, it has been necessary for the base rest 4, the outer enclosure (casing 2 and casing cover 3) and so forth to have a strong structure. In order to protect the inside radiation image detection panel 1 from any breakage caused by the casing cover 3 deforming and coming into contact with it, it is necessary to keep a large space between the casing cover 3 and the radiation image detection panel 1 (fluorescent plate). This hinders the imaging system from being made compact and light-weight. If, however, the casing cover 3 is made with an excessively large thickness to make it strong, the casing cover 3 may absorb significant radiation when the radiation pass through it, making the production of good images problematic.
The present invention was made in order to solve the above problems. Accordingly, an object of the present invention is to provide a radiation imaging system which enjoys properties of resistance to deformation under load, resistance to impact and resistance to vibration, and is compact and light-weight.
To achieve this object, the radiation imaging system of the present invention comprises a radiation image detection panel having means for converting radiation into electric signals, and an outer enclosure which holds therein the radiation image detection panel. An elastic support means elastically supports the radiation image detection panel relative to the outer enclosure.
With such a construction, even when a load is applied by the subject (patient) to the casing cover of the outer enclosure, deforming the casing cover, the radiation image detection panel can move toward the inside, acting against the elasticity of the elastic support means. Also, even impacts and vibrations occurring when the apparatus is carried can be absorbed by the elastic support means sufficiently that the panel can be prevented from breaking.
Details will become apparent from the description of the preferred embodiments below.